javascript - Ajax 响应 xml 为空 Java 脚本

Question

小服务程序响应：

for (int i = 0; i < projNames.size(); i++) {   
    sb.append("<project>");
    sb.append("<projectName>" + projNames.get(i) + "</projectName>");   
    sb.append("</project>");
    res.setContentType("text/xml");
    res.setHeader("Cache-Control", "no-cache");
    System.out.println(" test="+test);
    res.getWriter().write(sb.toString());
}

System.out.println 将“sb”值显示为

<project><projectName>sample</projectName></project><project><projectName>sample 2</projectName></project> 

我正在尝试检索响应 XML，但是当我检查长度时“对象值为 null”（在 IE 8 中调试）

function displayValues()
{
    var response;
    if (req.responseXML != null)
        alert("res xml is ther=="+ response); //displays UNDEFINED
    else
        alert("no res xml");

    response = req.responseXML.getElementsByTagName("project")[0];
    alert("child node"+response.childNodes.length); // alert is not displayed
} 

请赐教。谢谢

AJAX 代码：

<SCRIPT type="text/javascript">
var response;
var firstName;
var icdatevalue;
function getProject()
{ 
var url ="DBActionServlet?action=getProject"; 
            initRequest(url);
            req.onreadystatechange = processRequest;
            req.open("POST", url, true); 
            req.send(null);
                }
function initRequest(url) 
         {
            if (window.XMLHttpRequest) 
            {
                req = new XMLHttpRequest();
            } 
            else if (window.ActiveXObject) 
            {
                isIE = true;
                req = new ActiveXObject("Microsoft.XMLHTTP");
            }

         }

        function processRequest() 
         {
            if (req.readyState == 4) 
            {
                if (req.status == 200) 
            {

                    alert("status="+req.status);//status is shown as 200
                    displayValues(); //this function code mentioned above
                }
            }
         }

    </SCRIPT>